Some systems rely on multiple engines for producing mechanical power. For example, many aircraft (e.g., fixed-wing, rotorcraft, tilt-rotorcraft, etc.) rely on two or more engines to produce thrust. Mechanical deterioration and operational stresses endured by mechanical components of an engine may cause performance of that engine to degrade over time. Even if a multi-engine system commands each engine to provide approximately the same amount of mechanical power, each engine is inherently unique and may degrade at a different rate.
Eventually an engine may degrade to its respective end-of-life. Although other engines of the system may still possess useful life, a system may need to be taken offline each time a degraded engine needs to be serviced, overhauled, or replaced. To avoid having to take an entire system offline each time a single engine needs overhauling or replacing, a multi-engine system may replace all the engines while the system is offline, potentially wasting the useful life left in the other engines that do not necessarily need replacing.